Steerable ultrasound catheter

ABSTRACT

Ultrasound catheter devices and methods provide enhanced disruption of blood vessel obstructions. Ultrasound catheter devices generally include an elongate flexible catheter body with one or more lumens, an ultrasound transmission member extending longitudinally through the catheter body lumen and a distal head coupled with the transmission member and positioned adjacent the distal end of the catheter body for disrupting occlusions. Improved features of ultrasound catheters include catheter bodies and ultrasound transmission members with increasing distal flexibility, guidewire tubes allowing contact between a guidewire and an ultrasound transmission member, distal heads with improved guidewire lumens, and torquable proximal housings for enhancing disruption of blood vessel occlusions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. patent applicationSer. No. 12/021,082, filed Jan. 28, 2008, which is a divisional of U.S.patent application Ser. No. 10/722,209, filed Nov. 24, 2003 (now U.S.Pat. No. 7,335,180), entitled “Steerable Ultrasound Catheter.” Thisapplication is also related to the following U.S. patent applications,the full disclosures of which are all hereby incorporated by reference:U.S. patent application Ser. No. 10/229,371, filed Aug. 26, 2002 (nowU.S. Pat. No. 7,137,963), entitled “Ultrasound Catheter for DisruptingBlood Vessel Obstructions”; U.S. patent application Ser. No. 10/345,078,filed Jan. 14, 2003 (now U.S. Pat. No. 7,604,608), entitled “UltrasoundCatheter and Methods for Making and Using Same”; U.S. patent applicationSer. No. 10/375,903, filed Feb. 26, 2003 (now U.S. Pat. No. 6,942,677),entitled “Ultrasound Catheter Apparatus”; and U.S. patent applicationSer. No. 10/410,617, filed Apr. 8, 2003 (now U.S. Pat. No. 7,220,233),entitled “Improved Ultrasound Catheter Devices and Methods.”

BACKGROUND OF THE INVENTION

The present invention relates generally to medical devices and methods.More specifically, the present invention relates to ultrasound catheterdevices and methods for treating occlusive intravascular lesions.

Catheters employing various types of ultrasound transmitting membershave been successfully used to ablate or otherwise disrupt obstructionsin blood vessels. Specifically, ablation of atherosclerotic plaque orthromboembolic obstructions from peripheral blood vessels such as thefemoral arteries has been particularly successful. Various ultrasoniccatheter devices have been developed for use in ablating or otherwiseremoving obstructive material from blood vessels. For example, U.S. Pat.Nos. 5,267,954 and 5,380,274, issued to an inventor of the presentinvention and hereby incorporated by reference, describe ultrasoundcatheter devices for removing occlusions. Other examples of ultrasonicablation devices for removing obstructions from blood vessels includethose described in U.S. Pat. No. 3,433,226 (Boyd), U.S. Pat. No.3,823,717 (Pohlman, et at), U.S. Pat. No. 4,808,153 (Parisi), U.S. Pat.No. 4,936,281 (Stasz), U.S. Pat. No. 3,565,062 (Kuris), U.S. Pat. No.4,924,863 (Sterzer), U.S. Pat. No. 4,870,953 (Don Michael, et al), andU.S. Pat. No. 4,920,954 (Alliger, et at), as well as other patentpublications W087-05739 (Cooper), W089-06515 (Bernstein, et al.),W090-0130 (Sonic Needle Corp.), EP, EP316789 (Don Michael, et al.),DE3,821,836 (Schubert) and DE2438648 (Pohlman). While many ultrasoundcatheters have been developed, however, improvements are still beingpursued.

Typically, an ultrasonic catheter system for ablating occlusive materialincludes three basic components: an ultrasound generator, an ultrasoundtransducer, and an ultrasound catheter. The generator converts linepower into a high frequency current that is delivered to the transducer.The transducer contains piezoelectric crystals which, when excited bythe high frequency current, expand and contract at high frequency. Thesesmall, high-frequency expansions (relative to an axis of the transducerand the catheter) are amplified by the transducer horn into vibrationalenergy. The vibrations are then transmitted from the transducer throughthe ultrasound catheter via an ultrasound transmission member (or wire)running longitudinally through the catheter. The transmission membertransmits the vibrational energy to the distal end of the catheter wherethe energy is used to ablate or otherwise disrupt a vascularobstruction.

To effectively reach various sites for treatment of intravascularocclusions, ultrasound catheters of the type described above typicallyhave lengths of about 150 cm or longer. To permit the advancement ofsuch ultrasound catheters through small and/or tortuous blood vesselssuch as the aortic arch, coronary vessels, and peripheral vasculature ofthe lower extremities, the catheters (and their respective ultrasoundtransmission wires) must typically be sufficiently small and flexible.Also, due to attenuation of ultrasound energy along the long, thin,ultrasound transmission wire, a sufficient amount of vibrational energymust be applied at the proximal end of the wire to provide a desiredamount of energy at the distal end.

A number of ultrasound catheter devices have been described, for examplein U.S. patent application Ser. Nos. 10/229,371, 10/345,078, 10/375,903,and 10/410,617, which were previously incorporated by reference.Improvements, however, are always being sought. For example, itcontinues to be challenging to develop a catheter that is stiff enoughto be pushable or “steerable” through vasculature yet flexible enough,at least along part of its length, to navigate small, tortuous bloodvessels, such as the coronary arteries or tortuous peripheralvasculature. It is also sometimes difficult to manipulate currentlyavailable ultrasound catheter devices, for example to twist or torquethe proximal end of the catheter to move the distal end in a way thathelps with navigation through the vasculature. Passage of a guidewirethrough an ultrasound catheter may also be improved upon, such that theguidewire does not interfere with, and may even enhance, disruption ofvascular occlusions.

Therefore, a need exists for improved ultrasound catheter devices andmethods that provide ablation or disruption of vascular occlusions.Ideally, such ultrasound catheters would have enhanced ability tonavigate through small, tortuous blood vessels such as the coronaryarteries. It would also be advantageous to have catheters that could beeasily manipulated by a user. Ideally, such devices would allow forpassage of a guidewire without interfering with, and perhaps evenenhancing, disruption of vascular occlusions. At least some of theseobjectives will be met by the present invention.

BRIEF SUMMARY OF THE INVENTION

Ultrasound catheter devices and methods provide enhanced disruption ofblood vessel obstructions. Generally, ultrasound catheters include anelongate flexible catheter body with one or more lumens, an ultrasoundtransmission member extending longitudinally through the catheter bodylumen, and a distal head coupled with the transmission member andpositioned adjacent the distal end of the catheter body for disruptingocclusions. Improved features include but are not limited to catheterbodies and ultrasound transmission members with increasing flexibilitytoward their distal ends, devices that bend concomitantly with one ormore bends in a guidewire and/or a blood vessel, a proximal housingcoupled with an ultrasound catheter body for enhancing manipulation ofthe catheter body, a guidewire lumen configured to allow contact betweena guidewire and an ultrasound transmission member, distal heads withimproved guidewire lumens and the like.

In one aspect of the present invention, an ultrasound catheter fordisrupting occlusions in blood vessels is provided, which can be guidedfrom an access site on a patient's body to a target site adjacent anocclusion. The ultrasound catheter generally includes an elongateflexible catheter body, an ultrasound transmission member extendinglongitudinally through the lumen of the catheter body, a distal headcoupled with the distal end of the ultrasound transmission member anddisposed adjacent the distal end of the catheter body, and at least onecoupling member for coupling the ultrasound transmission member with asource of ultrasound energy. The catheter body has a proximal portion, adistal portion and at least one lumen, the proximal portion beingstiffer than the distal portion, and the distal portion being moreflexible near the distal end of the catheter body than near the proximalportion of the catheter body. The ultrasound transmission member has aproximal end and a distal end and is more flexible near its distal endthan near its proximal end. Thus, both the distal portion of thecatheter body and the ultrasound transmission member are more flexibletoward the distal end of the device.

The increasing flexibility of the catheter body and the ultrasoundtransmission wire toward the distal end of the catheter device may beachieved by any suitable fabrication method. In some embodiments, forexample, the ultrasound transmission wire, catheter body, or both may betapered, such that their cross-sectional diameters decrease distally. Inone embodiment, for example, the cross-sectional diameter of a catheterbody may range from between about 0.102 cm and about 0.178 cm along itsproximal end to between about 0.076 cm and about 0.127 cm along itsdistal end, and the cross-sectional diameter of an ultrasoundtransmission member may range from between about 0.051 cm and about0.102 cm near its proximal end to between about 0.013 cm and about 0.038cm near its distal end. Additionally or alternatively, the wallthickness of the catheter body may decrease from proximal to distal. Forexample, in one embodiment, the wall thickness of a catheter body maymeasure about 0.007 cm to about 0.020 cm along its proximal portion andabout 0.005 cm to about 0.013 cm along its distal portion. In these orother embodiments, various combinations of materials may be used to givethe catheter body, transmission wire or both a desired flexibilityprofile. Providing an ultrasound catheter with a catheter body andultrasound transmission wire that both increase in flexibility towardthe distal end of the device will enhance navigation of the distal endof the device through tortuous blood vessels. In one embodiment, forexample, the distal portion of the device will be sufficiently flexibleto pass, without kinking, through at least 5 cm length of a blood vesselhaving at least one bend and an inner diameter of between about 2 mm andabout 5 mm. A “tortuous vessel,” for the purposes of this application,means having at least one bend or curve, and the bend or curve may haveany angle or radius of curvature. In some embodiments, for example, atleast one bend in a vessel may have a radius of about 1.0 cm or less. Insome instances, of course, a tortuous blood vessel will have multiplebends or curves.

In another aspect of the invention, an ultrasound catheter fordisrupting occlusions in blood vessels which can be guided along aguidewire from an access site on a patient's body to a target siteadjacent an occlusion includes an elongate flexible catheter body, anultrasound transmission member extending longitudinally through thelumen of the catheter body, a distal head coupled with the distal end ofthe ultrasound transmission member and disposed adjacent the distal endof the catheter body, and at least one coupling member for coupling theultrasound transmission member with a source of ultrasound energy. Inthis aspect, the catheter body has a proximal portion, a distal portionand at least one lumen, the proximal portion has a largercross-sectional diameter than the distal portion, the proximal portionis sufficiently stiff to push the distal portion through a blood vesselhaving at least one bend, and the distal portion is sufficientlyflexible to pass through the bend in the blood vessel. The ultrasoundtransmission member has a proximal end and a distal end, thecross-sectional diameter of the ultrasound transmission member is lessnear its distal end than near its proximal end, and a distal portion ofthe ultrasound transmission member is sufficiently flexible to passthrough the bend in the blood vessel. Again, in some embodiments thewall of the catheter body may be thinner along the distal portion thanalong the proximal portion.

In another aspect of the present invention, an ultrasound catheter fordisrupting occlusions in blood vessels which can be guided from anaccess site on a patient's body to a target site adjacent an occlusionincludes an elongate flexible catheter body having a proximal portion, adistal portion and at least one lumen, an ultrasound transmission memberextending longitudinally through the lumen of the catheter body, adistal head coupled with the distal end of the ultrasound transmissionmember and disposed adjacent the distal end of the catheter body, and atleast one coupling member for coupling the ultrasound transmissionmember with a source of ultrasound energy. In this aspect, the distalportion of the catheter body is more flexible near a distal end of thecatheter body than near the proximal portion of the catheter body, andthe ultrasound transmission member is more flexible near its distal endthan near its proximal end. Additionally, the distal portion of thecatheter body and the ultrasound transmission member are sufficientlyflexible to conform concomitantly with at least one bend in a guidewireextended through the at least one lumen.

By “conforming concomitantly” it is meant that the catheter body and theultrasound transmission member conform to the at least one bend in theguidewire such that the catheter body, transmission member and guidewirebend at an approximately similar angle. In some embodiments, the distalportion of the catheter body and the ultrasound transmission wire aresufficiently flexible to conform concomitantly to multiple bends in theguidewire. Also in some embodiments, the distal portion of the catheterbody and the ultrasound transmission member are sufficiently flexible toconform concomitantly to multiple bends in a blood vessel. In variousembodiments, the catheter may be advanced over a guidewire, a guidewiremay be passed through the catheter body, or the catheter body,ultrasound transmission wire and guidewire may be advanced through ablood vessel simultaneously. Thus, in various embodiments, the distalportion of the catheter body, the ultrasound transmission wire and theguidewire may be passed together or sequentially through the multiplebends in the blood vessel while conforming concomitantly to the multiplebends.

In another aspect of the present invention, an ultrasound catheter fordisrupting occlusions in blood vessels which can be guided from anaccess site on a patient's body to a target site adjacent an occlusionincludes an elongate flexible catheter body having a proximal portion, adistal portion and at least one lumen, an ultrasound transmission memberextending longitudinally through the lumen of the catheter body, adistal head coupled with the distal end of the ultrasound transmissionmember and disposed adjacent the distal end of the catheter body, and atleast one coupling member for coupling the ultrasound transmissionmember with a source of ultrasound energy. In this aspect, the distalportion of the catheter body has at least one bend, and at least onelumen, the proximal portion of the catheter body is stiffer than thedistal portion, and the distal portion is more flexible near a distalend of the catheter body than near the proximal portion of the catheterbody. The ultrasound transmission member is more flexible near itsdistal end than near its proximal end, the ultrasound transmissionmember conforms to the at least one bend in the distal portion of thecatheter body, and the distal portion of the catheter body and theultrasound transmission member are sufficiently flexible to conformconcomitantly to at least one bend in a guidewire.

In still another aspect of the present invention, an ultrasound catheterfor disrupting occlusions in blood vessels which can be guided from anaccess site on a patient's body to a target site adjacent an occlusionincludes an elongate flexible catheter body having a proximal portion, adistal portion and at least one lumen, an ultrasound transmission memberextending longitudinally through the lumen of the catheter body, adistal head coupled with the distal end of the ultrasound transmissionmember and disposed adjacent the distal end of the catheter body, and atleast one coupling member for coupling the ultrasound transmissionmember with a source of ultrasound energy. In this aspect, the catheterbody includes a guidewire tube disposed within the lumen, and theproximal portion of the body is stiffer than the distal portion. Theguidewire tube includes at least one opening within the catheter bodyfor providing contact between a guidewire extending through theguidewire tube and the ultrasound transmission member.

Allowing a guidewire to contact the ultrasound transmission member mayfacilitate passage of the guidewire into or through a vascularocclusion, by allowing a portion of the ultrasound energy transmitted bythe transmission member to be transferred to the guidewire. In variousembodiments, the guidewire may contact the transmission member near theproximal end of the catheter device, near the distal end, near themiddle, or some combination thereof. In some embodiments, the guidewiretube includes two openings within the catheter body, to allow thetransmission member to pass through the tube. Any other configurationfor allowing contact between a guidewire and the ultrasound transmissionmember is also contemplated.

In another aspect of the present invention, an ultrasound catheter fordisrupting occlusions in blood vessels which can be guided from anaccess site on a patient's body to a target site adjacent an occlusionincludes an elongate flexible catheter body having a proximal portion, adistal portion and at least one lumen, an ultrasound transmission memberextending longitudinally through the lumen of the catheter body, adistal head coupled with the distal end of the ultrasound transmissionmember and disposed adjacent the distal end of the catheter body, and atleast one coupling member for coupling the ultrasound transmissionmember with a source of ultrasound energy. In this aspect, the distalhead includes a guidewire aperture in the center of its distal end and aguidewire lumen extending through the distal head. The guidewire lumen,in tum, has a different longitudinal axis than the longitudinal axis ofthe catheter body.

Having a guidewire lumen that exits from the center of the distal headis advantageous for advancing the guidewire as well as the catheterdevice. Angling the guidewire lumen away from the longitudinal axis ofthe catheter body allows a guidewire and the ultrasound transmissionmember to pass through a narrower catheter body, thus decreasing thediameter of the catheter device and facilitating passage throughtortuous vessels. In some embodiments, the guidewire lumen in the distalhead includes a cavity in which a distal end of a guidewire tube of thecatheter body is disposed. In some embodiments, the cavity extendsthrough the distal end of the distal head, such that the distal end ofthe guidewire tube is flush with the distal end of the distal head. Inother embodiments, the cavity extends partially through the distal head,such that the distal end of the guidewire tube is disposed proximal tothe distal end of the distal head.

In another aspect of the present invention, an ultrasound catheter fordisrupting occlusions in blood vessels which can be guided from anaccess site on a patient's body to a target site adjacent an occlusionincludes an elongate flexible catheter body having a proximal portion, adistal portion and at least one lumen, an ultrasound transmission memberextending longitudinally through the lumen of the catheter body, adistal head coupled with the distal end of the ultrasound transmissionmember and disposed adjacent the distal end of the catheter body, and atleast one coupling member for coupling the ultrasound transmissionmember with a source of ultrasound energy. In this aspect of theinvention, the at least one coupling member comprises a housing fixedlycoupled with the proximal end of the catheter body such that torqueapplied to the housing is transmitted along the catheter body to itsdistal portion.

In yet another aspect of the invention, a method for disrupting anocclusion in a blood vessel involves: advancing an ultrasound catheterthrough a blood vessel having at least one bend, the catheter conformingconcomitantly to the at least one bend, wherein advancing includescontacting an ultrasound transmission member of the ultrasound catheterwith a guidewire at one or more locations within the catheter;positioning a distal end of the ultrasound catheter adjacent anocclusion in the blood vessel; and transmitting ultrasound energy to theultrasound transmission member to disrupt the occlusion into multipleocclusion fragments, wherein transmitting includes transmittingultrasound energy to the guidewire. Optionally, the method may furtherinclude removing at least some of the occlusion fragments from the bloodvessel via the ultrasound catheter. In some embodiments, the ultrasoundcatheter is advanced along the guidewire. Alternatively, the guidewiremay be passed through the catheter, or the catheter and the guidewiremay be advanced together through the blood vessel. Positioning may alsoinvolve advancing the ultrasound catheter and the guidewire alongmultiple bends in the blood vessel, wherein a catheter body of thecatheter, the ultrasound transmission member and the guidewire conformconcomitantly to the multiple bends. Bends may have any suitable angleor radius of curvature. In one embodiment, for example, one or morebends may have a radius of about 1.0 cm or less. The method may alsoinvolve applying radial force to a proximal housing of the ultrasoundcatheter to radially tum the distal end of the ultrasound catheter inthe blood vessel.

Further aspects and specific embodiments of the invention will bedescribed below, in reference to the attached drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an ultrasound catheter system includingan ultrasound catheter device and ultrasound energy source according toan embodiment of the present invention;

FIG. 1A is a cross-sectional side view of an ultrasound catheter deviceaccording to one embodiment of the present invention;

FIG. 2 is a perspective view of a human heart and an ultrasound catheterdevice, showing one possible path along which a device may be advancedaccording to an embodiment of the present invention;

FIG. 3 is a cross-sectional side view of a portion of an ultrasoundcatheter device according to an embodiment of the present invention;

FIG. 4 is a cross-sectional side view of a distal portion of anultrasound catheter device and a guidewire according to an embodiment ofthe present invention;

FIG. 5 is a cross-sectional side view of a distal portion of anultrasound catheter device and a guidewire according to an embodiment ofthe present invention;

FIG. 6 is a cross-sectional side view of the distal end of theultrasound catheter device and a guidewire shown in FIG. 5;

FIG. 7 is a cross-sectional side view of a distal end of an ultrasoundcatheter device and a guidewire according to an embodiment of thepresent invention; and

FIG. 8 is a perspective view of an ultrasound catheter device having afixed proximal housing according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Ultrasound catheter devices and methods of the present inventiongenerally provide for enhanced treatment of occlusive intravascularlesions. Catheter devices generally include a catheter body, anultrasound energy transmission member disposed within the catheter bodyand a distal head coupled with the energy transmission member anddisposed adjacent the distal end of the catheter body. The ultrasoundtransmission member transmits ultrasound energy from an ultrasoundtransducer to the distal head, causing the head to vibrate and, thus,disrupt vascular occlusions. A number of improved features of suchultrasound catheter devices are described more fully below.

Referring now to FIG. 1, one embodiment of an ultrasound catheter system20 suitably includes an ultrasound catheter device 10, including aproximal end connector 12 for coupling device 10 with an ultrasoundtransducer 14, and an ultrasound generator 16 coupled with transducer 14and a foot-actuated on/off switch 18 to provide ultrasonic energy totransducer 14 and, thus, to ultrasound catheter 10. Generally, catheter10 includes an ultrasound transmission member, or wire (not shown), fortransmitting energy from the transducer 14 to a distal head 26 ofcatheter 10. In some embodiments, transducer 14 further includes asecuring device 15 for enhancing coupling of catheter 10 to transducer14. Components of system 20 may be coupled via any suitable means, suchas connecting wires of any kind, wireless connections or the like.

In addition to proximal connector 12, ultrasound catheter device 10 mayinclude one or more other various components, such as a Y-connector 11or the like for providing access for irrigation, guidewire passage,suction or the like. Some embodiments of device include a monorailguidewire 13, some include a proximal guidewire port 17 for over thewire guidewire delivery, and some embodiments include both. In someembodiments, Y-connector may include an irrigation port, for providingaccess for an irrigation tube 24. Irrigation tube 24, in someembodiments, may be used for introducing one or more fluids, applyingvacuum, or both. Generally, catheter device 10 may include any suitablenumber of side-arms or ports for passage of a guidewire, infusing and/orwithdrawing irrigation fluid, dye and/or the like, or any other suitableports or connections. Also, ultrasound catheters 10 of the presentinvention may be used with any suitable proximal devices, such as anysuitable ultrasound transducer 14, ultrasound generator 16, couplingdevice(s) and/or the like. Therefore, exemplary FIG. 1 and any followingdescriptions of proximal apparatus or systems for use with ultrasoundcatheters 10 should not be interpreted to limit the scope of the presentinvention as defined in the appended claims.

Referring now to FIG. 1A, a cross-sectional side view of one embodimentof ultrasound catheter device 10 is shown. Generally, ultrasoundcatheter 10 suitably includes an elongate catheter body 22 with anultrasound transmission member 24 disposed longitudinally through acatheter lumen 21 and ending in distal head (not shown). Catheter body22 is generally a flexible, tubular, elongate member, having anysuitable diameter and length for reaching a vascular occlusion fortreatment. In one embodiment, for example, catheter body 22 preferablyhas an outer diameter of between about 0.5 mm and about 5.0 mm. In otherembodiments, as in catheters intended for use in relatively smallvessels, catheter body 22 may have an outer diameter of between about0.25 mm and about 2.5 mm. Catheter body 22 may also have any suitablelength. As discussed briefly above, for example, some ultrasoundcatheters have a length in the range of about 150 cm. However, any othersuitable length may be used without departing from the scope of thepresent invention. Examples of catheter bodies similar to those whichmay be used in the present invention are described in U.S. Pat. Nos.5,267,954 and 5,989,208, which were previously incorporated herein byreference.

In some embodiments, catheter body 22 is made from a polymeric material.Sometimes the polymer will have a desired amount of flexibility, such asin one embodiment where catheter body 22 is made of a polymer having aflexural modulus of less than about 160 Psi. In some embodiments, such apolymer will be one of any number of polyether block amides, althoughother polymers may of course be used. In some embodiments, suchpolyether block amides may have a Shore D hardness value ranging fromabout 55 to about 75, while in other embodiments they may have a Shore Dhardness value ranging from about 25 to about 55. In some embodiments,the polymeric material includes up to about 5 weight percent of acolorant.

In most embodiments, ultrasound transmission member 24, which maycomprise a wire, wave guide or the like, extends longitudinally throughcatheter body lumen 21 to transmit ultrasonic energy from ultrasoundtransducer 14 (FIG. 1) to the distal end of catheter 10. Ultrasoundtransmission member 24 may be formed of any material capable ofeffectively transmitting ultrasonic energy from ultrasound transducer 14to the distal end of catheter body 22, including but not limited tometals such as pure titanium or aluminum, or titanium or aluminumalloys. In accordance with one aspect of the invention, all or a portionof ultrasound transmission member 24 may be formed of one or morematerials which exhibit superelastic properties. Such material(s) shouldpreferably exhibit superelasticity consistently within the range oftemperatures normally encountered by ultrasound transmission member 24during operation of ultrasound catheter apparatus 10. For example, insome embodiments, the material is an alloy having a tensile strength ofbetween about 170,000 Psi and about 250,000 Psi. In some embodiments,the alloy exhibits elongation of between about 7% and about 17%. Forexample, in some embodiments the alloy is a nickel-titanium alloy havingnickel content of between about 50.50 and about 51.50 atomic weight.

Use of superelastic metal alloys in ultrasound transmission members isdescribed in U.S. Pat. No. 5,267,954, previously incorporated byreference. Examples of superelastic metal alloys which may be used aredescribed in detail in U.S. Pat. No. 4,665,906 (Jervis); U.S. Pat. No.4,565,589 (Harrison); U.S. Pat. No. 4,505,767 (Quin); and U.S. Pat. No.4,337,090 (Harrison), the entire disclosures of which are herebyincorporated by reference insofar as they describe the compositions,properties, chemistries and behavior of specific metal alloys which aresuperelastic within the temperature range at which ultrasoundtransmission member 24 of the present invention operates, any and all ofwhich superelastic metal alloys may be used to form ultrasoundtransmission member 24 of the present invention. In some embodiments,for example, the alloy exhibits a superelastic temperature range ofabout 10 degrees Celsius to about 50 degrees Celsius.

With continued reference to FIG. 1A, one embodiment of proximal endconnector 12 suitably includes a housing 42 with a hollow inner bore 44.Bore 44 may have a uniform inner diameter along its length or,alternatively, may have multiple segments, such as a proximal segment47, a middle segment 45 and a distal segment 49, each of which maysurround one or more various components of proximal end connector 12.Generally, proximal segment 47 of bore 44 is configured to allowcoupling with ultrasound transducer 14 (not shown) via any suitablecoupling means, such as a pressure fit, complementary threads or thelike. Proximal segment 47 includes a sonic connector 52 for transmittingvibrational energy from transducer 14 to ultrasound transmission member24. Sonic connector 52 may be held within housing 42 by any suitablemeans. In some embodiments, for example, a dowel pin may extend throughsonic connector 52 to hold it within housing 42. In another embodiment,sonic connector 52 may be secured within housing 42 by means of a cavityin housing 42.

Middle segment 45 of bore 44, in some embodiments, may surround aportion of sonic connector 52, while in other embodiments, sonicconnector 52 may be housed only within proximal segment 47. Sonicconnector 52 is coupled with the proximal end of ultrasound transmissionmember 24 by any suitable means for transmitting ultrasound energy totransmission member 24 from transducer 14. Absorber members 50, such asO-rings, surround a portion of ultrasound transmission member 24 forproviding absorption of transverse vibration. Absorber members 50 may beused in any number or combination and have any suitable size andconfiguration, depending on the desired level of vibration absorption ordampening. Alternatively or additionally, other dampening structures maybe used. Thus, the invention is not limited to the combination shown inFIG. 1A.

Distal segment 49 of bore 44 typically surrounds a portion of ultrasoundtransmission member 24 and may also contain one or more additional setsof absorber members 50. Distal segment 49 may also contain a portion ofa Y-connector 11, which is coupled with the distal end of housing 42.Coupling of Y -connector 11 with the distal end of housing 42 may beaccomplished via complementary threads, pressure fitting, or any othersuitable means. A Y-connector lumen 48 of Y-connector 11 allows passageof ultrasound transmission member 24 and is in fluid communication withcatheter body lumen 21.

Generally, pressurized fluid such as a coolant liquid may be infusedthrough a sidearm 13 of Y-connector, through Y-connector lumen 48 andthrough catheter body lumen 21 so that it flows out of one or more fluidoutflow apertures in distal head 26. The temperature and flow rate ofsuch coolant liquid may be specifically controlled to maintain thetemperature of ultrasound transmission member 24 at a desiredtemperature within its optimal working range. In particular, inembodiments of the invention wherein ultrasound transmission member 24is formed of a metal alloy which exhibits optimal physical properties(e.g. super elasticity) within a specific range of temperatures, thetemperature and flow rate of coolant liquid infused through fluidinfusion side-arm 13 may be specifically controlled to maintain thetemperature of ultrasound transmission member 24 within a range oftemperatures at which it demonstrates its most desirable physicalproperties. For example, in embodiments of the invention whereinultrasound transmission member 24 is formed of a shape memory alloywhich exhibits super elasticity when in its martensite state, but whichloses super elasticity as it transitions to an austenite state, it willbe desirable to adjust the temperature and flow rate of the coolantliquid infused through fluid infusion side-arm 13 so as to maintain theshape memory alloy of ultrasound transmission member 24 within atemperature range at which the alloy will remain in its martensite stateand will not transition to an austenite state. The temperature at whichsuch shape memory alloys transition from a martensite state to anaustenite state is known as the “martensite transition temperature” ofthe material. Thus, in these embodiments, the fluid infused throughside-arm 13 will be at such temperature, and will be infused at suchrate, as to maintain the shape memory alloy of ultrasound transmissionmember 24 below its martensite transition temperature.

Referring now to FIG. 2, an ultrasound catheter device 100 may be usedin to treat one or more coronary arteries CA in a human heart H. Someembodiments include a flexible distal portion configured to navigate oneor more bends 102 in a coronary artery CA or other vessel. In someembodiments, catheter device 100 will be positioned in a coronary arteryCA or other vessel by advancing it over (or along with) a guidewire 104.Some embodiments may also include or be used with a guide catheter 106.

As mentioned above, a “tortuous blood vessel,” for the purposes of thisapplication, means a vessel having at least one bend (which may also bereferred to as a “curve” or the like), having any angle of curvature. Insome cases, of course, tortuous vessels also have relatively small innerdiameters and multiple bends, and various embodiments of ultrasoundcatheter device 100 are configured to navigate multiple bends in avessel. In some embodiments, ultrasound catheter device 100 isconfigured to conform to one or more bends in a vessel such that two ormore components of the device bend concomitantly with one another. Forexample, in some embodiments, when device 100 extends through a bend ina vessel, an ultrasound transmission member and a catheter body ofdevice 100 will bend with approximately the same angle. In someembodiments, the ultrasound transmission member, the catheter body and aguidewire extending through the catheter may all bend concomitantly toconform to a bend in a blood vessel. Such concomitant bending is incontrast with some prior art devices, wherein the ultrasoundtransmission member, for example, is relatively stiffer than a distalportion of the catheter body, so that when the device is placed in abend in a blood vessel, the catheter body bends at a more acute anglethan the transmission member.

Referring now to FIG. 3, in one embodiment an ultrasound catheter device110 of the present invention includes a catheter body 116 having aproximal portion 112 and a distal portion 114, an ultrasoundtransmission member 118, and a distal head Ill. As discussed above,catheter body 116, transmission member 118 and distal head 111 may befabricated from any suitable material(s) and may have any of a number ofsuitable configurations, dimensions, and the like. In fact, FIG. 3 isnot drawn to scale, and distal portion 114, for example, may berelatively much longer than shown in FIG. 3.

Proximal portion 112 of catheter body 116 is generally stiffer thandistal portion 114, such proximal portion 112 is used for pushing orsteering, and distal portion 114 is sufficiently flexible to navigatethrough a tortuous blood vessel to reach an occlusion site. Thedifference in stiffness/flexibility may be achieved by using differentmaterials for the different portions, by configuring proximal portion112 with a thicker wall than distal portion 114, by giving proximalportion 112 a larger outer diameter, any combination of these, or anyother suitable technique. In some embodiments, proximal portion 112 anddistal portion 114 are made from one piece of material, or oneextrusion, while in other embodiments two or more pieces of material maybe joined together. Ultrasound transmission member 118 also becomes moreflexible (less stiff) toward its distal end. This is typically achievedby tapering transmission member 118, and the taper may be gradual, asshown in FIG. 3, or may be achieved in one or more less-gradual steps.By providing catheter body 116 and ultrasound transmission member 118with progressively increasing flexibility toward the distal end,catheter device 110 may provide enhanced “pushability” or“steerability,” while also facilitating navigation of tortuous vesselswith distal portion 114.

With reference now to FIG. 4, another embodiment of an ultrasoundcatheter device 120 includes a catheter body 126, an ultrasoundtransmission member 128 and a guidewire tube 124 disposed within body126, and a distal head coupled with ultrasound transmission member 121.Guidewire tube 124 may enter catheter body 126 at any suitable locationand may extend distally up to, partially through, or completely throughdistal head 121, as will be explained more fully below. In oneembodiment, guidewire tube 124 includes at least one opening 125disposed within catheter body 126, for allowing a guidewire 122 tocontact ultrasound transmission member 128 at one or more locations. Inthe embodiment shown, guidewire tube 124 includes two openings 125 toallow ultrasound transmission member 128 to pass through tube 124. Anyother suitable opening(s) is also contemplated within the scope of theinvention. By allowing guidewire 122 to contact ultrasound transmissionmember 128, an amount of ultrasound energy may be transferred fromtransmission member 128 to guidewire 122. This transferred energy maycause guidewire 122 to vibrate, and such vibrational energy may enhancethe ability of guidewire 122 to cross a vascular occlusion. In manyprocedures, it is often advantageous to penetrate or cross an occlusionwith guidewire 122, and utilizing ultrasound energy transferred toguidewire 122 from transmission member 128 will enhance such procedures.

Referring now to FIGS. 5 and 6, another embodiment of an ultrasoundcatheter device 130 suitably includes a catheter body 136, an ultrasoundtransmission member 138 and a guidewire tube 134 disposed withincatheter body 136, and a distal head 131 coupled with the distal ends oftransmission member 128 and guidewire tube 134. In this embodiments,distal head 131 includes a guidewire lumen 135. Guidewire lumen 135 hasa cavity at its proximal end for accepting the distal end of guidewiretube 134. In alternative embodiments, distal head 131 may not include acavity, and guidewire tube 134 may abut the proximal end of distal head131, or the cavity may extend all the way through distal head 131, sothat guidewire tube 134 extends all the way through distal head 131 andis flush with the distal end of distal head 131. Also in the embodimentdepicted in FIGS. 5 and 6, guidewire lumen 135 of distal head 131 has alongitudinal axis 139 which is not parallel to the overall longitudinalaxis 137 of catheter device 130. Thus, at least a distal portion ofguidewire tube 134 is also disposed on the longitudinal axis 139 that isnot parallel to the catheter device's 130 longitudinal axis 137. At thesame time, guidewire lumen 135 of distal head 131 exits approximately atthe center of the distal end of distal head 131. Typically, it isadvantageous to have guidewire 132 exit approximately the center ofdistal head 131, to facilitate tracking of catheter device 130 alongguidewire 132. It may also be advantageous, however, to offset guidewiretube 134 within catheter body 136, so that guidewire tube 134 andultrasound transmission member 138 may fit within a catheter body havinga smaller inner diameter. Smaller diameter catheters, of course, aremore easily advanced through tortuous vasculature.

Generally, any coupled components described above may be coupled by anysuitable means, such as adhesives, complementary threaded members,pressure fittings, and the like. For example, distal head 131 may becoupled with ultrasound transmission member 138, guidewire tube 134,and/or catheter body 136 with any suitable adhesive substance or viawelding, bonding, pressure fitting, threaded fittings or the like.Adhesives may include, but are not limited to cyanoacrylate (eg.Loctite™, Loetite Corp., Ontario, CANADA or Dron Alpha™, Borden, Inc.,Columbus, Ohio) or polyurethane (e.g. Dymax™, Dymax EngineeringAdhesive, Torrington, Conn.) adhesives. Some embodiments may alsoinclude one or more anchoring members for further securing distal head131 to the ultrasound catheter device 130. Examples of such anchoringmembers are described more fully in U.S. patent application Ser. No.10/410,617, which was previously incorporated by reference.

Referring now to FIG. 7, another embodiment of an ultrasound catheterdevice 140 includes a catheter body 146, ultrasound transmission member148, guidewire tube 144 and distal head 141 having a guidewire lumen145. In this embodiment, as mentioned briefly above, guidewire lumen 145is configured such that guidewire tube 144 extends through the wholelength of distal head 141 and ends flush with the distal end of distalhead 141. Generally, distal head 141 and guidewire lumen 145 may haveany suitable sizes, shapes, configurations, dimensions and the like, andthe invention is in no way limited by the embodiments shown.

With reference now to FIG. 8, some embodiments of an ultrasound catheterdevice 150 include a proximal housing 152 that is fixedly coupled with acatheter body 156. Housing 152 may be a handle, a coupling member forcoupling the device 150 to an ultrasound transducer, or any othersuitable proximal device for allowing a user to manipulate catheterdevice 150. By providing fixed coupling between housing 152 and catheterbody, a proximal rotational force 155 a (or torque, or twisting) appliedat housing 152 will be transmitted to catheter body 156 to cause thedistal end of catheter body 156 and distal head 151 to rotate 155 b. Ithas been found that torquing, twisting or rotating ultrasound catheterdevice 150 may facilitate navigation of the device through tortuousvasculature and/or dissolution of a vascular occlusion using the device.

Although the invention has been described above with specific referenceto various embodiments and examples, it should be understood thatvarious additions, modifications, deletions and alterations may be madeto such embodiments without departing from the spirit or scope of theinvention. Accordingly, it is intended that all reasonably foreseeableadditions, deletions, alterations and modifications be included withinthe scope of the invention as defined in the following claims.

What is claimed is:
 1. An ultrasound catheter comprising: a catheterbody having a proximal portion, a distal portion and a lumen; anultrasound transmission member extending longitudinally through thelumen of the catheter body and having a distal end; a distal headcoupled with the distal end of the ultrasound transmission member anddisposed adjacent the distal portion of the catheter body; a guidewirelumen extending through the distal head, the guidewire lumen having asmaller diameter portion at a distal end and a larger diameter portionat a proximal end, the larger diameter portion forming a cavity in thedistal head; and a guidewire tube extending through at least a portionof the catheter body and the distal head, a distal end of the guidewiretube being disposed in the cavity in the distal head.
 2. The ultrasoundcatheter of claim 1, wherein the guidewire tube is coupled to the distalhead in the cavity.
 3. The ultrasound catheter of claim 1, wherein theexterior surface of the guidewire tube is coupled to an interior wall ofthe cavity.
 4. The ultrasound catheter of claim 1, wherein the guidewiretube comprises an exterior surface and a distal edge.
 5. The ultrasoundcatheter of claim 4, wherein the distal edge of the guidewire tube iscoupled to an abutment surface formed at the distal end of the cavity.6. The ultrasound catheter of claim 5, wherein the abutment surfaceextends circumferentially around the guidewire lumen.
 7. The ultrasoundcatheter of claim 1, wherein the guidewire tube extends through thedistal head in a distal direction beyond the distal end of theultrasound transmission member.
 8. The ultrasound catheter of claim 1further comprising at least one coupling member for coupling theultrasound transmission member with a source of ultrasound energy. 9.The ultrasound catheter of claim 1, wherein the guidewire tube entersthe lumen of the catheter body at an entry point that is proximal to thedistal head and distal to the proximal portion of the catheter body. 10.The ultrasound catheter of claim 9, wherein the exterior surface of theguidewire tube is coupled with the catheter body at the entry point. 11.An ultrasound catheter comprising: a catheter body having a proximalportion, a distal portion and a lumen; an ultrasound transmission memberextending longitudinally through the lumen of the catheter body; adistal head having a proximal end and a distal end, the distal headbeing coupled with the ultrasound transmission member and disposedadjacent to the distal portion of the catheter body; a guidewire lumenextending through the distal head; and a guidewire tube comprising anexterior surface and a distal edge, the guidewire tube extending throughthe lumen of the catheter body and the guidewire lumen so that thedistal edge of the guidewire tube abuts the distal end of the distalhead.
 12. The ultrasound catheter of claim 11, wherein the guidewiretube is coupled to the distal head in the guidewire lumen.
 13. Theultrasound catheter of claim 11, wherein the exterior surface of theguidewire tube is coupled to an interior wall of the guidewire lumen.14. The ultrasound catheter of claim 11, wherein the guidewire tubeextends through the distal head distally beyond the ultrasoundtransmission member.
 15. The ultrasound catheter of claim 11 furthercomprising at least one member for coupling the ultrasound transmissionmember with a source of ultrasound energy.
 16. The ultrasound catheterof claim 11, wherein the guidewire tube enters the lumen of the catheterbody at an entry point that is proximal to the distal head and distal tothe proximal portion of the catheter body.
 17. The ultrasound catheterof claim 16, wherein the exterior surface of the guidewire tube iscoupled with the catheter body at the entry point.
 18. An ultrasoundcatheter comprising: a catheter body having a proximal portion, a distalportion and a lumen; an ultrasound transmission member disposed in thecatheter body; and a head coupled to the ultrasound transmission memberand having a guidewire lumen, the guidewire lumen forming an abutmentsurface in the head so as to contact an end of a guidewire tube toprevent movement of the guidewire tube in at least one directionrelative to the head.
 19. The ultrasound catheter of claim 18 furthercomprising a guidewire tube, the guidewire tube being disposed in theguidewire lumen.
 20. The ultrasound catheter of claim 18 furthercomprising a guidewire, the guidewire being disposed in the guidewiretube.